IF the original glue bond is wood to cardboard/paper with wood glue or white glue, then the best thing is just to bend the fin back a bit to open up the crack a bit, and use whatever method works for you to squeeze more glue in there. Then get the fin back into position and tape or clamp it into place. Wipe off excess glue, allow to dry overnight before doing anything else. This should restore it to pretty much original strength.
Avoid ripping it off, as it is less likely you will get it positioned exactly where it should be.
I've got a Mars Snooper in my build pile. The BMS clone. Where did yours come from?
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